Dynamics of a tidally-forced stratified shear flow on the continental slope

Cynthia Bluteau, Nicole Jones, Gregory Ivey

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

The near seabed mean and turbulent processes on the continental slope were measured for a three week period using an array of acoustic-Doppler velocimeters and thermistors over the bottom 30 m at the 400 m isobath. Baroclinic motions with characteristics similar to internal bores or boluses propagated onshore during the flood phase of both spring and neap tides. The arrival time of these internal bores at our measurement site varied amongst tidal cycles and their characteristics were not highly correlated with the amplitude of the barotropic tidal forcing. The passage of the internal bores was associated with large turbulent overturns, enhanced turbulent kinetic energy dissipation (epsilon > 10(-6) W kg(-1)) and intensified currents (>6 times the barotropic forcing) within meters of the seabed. During the deployment, stratification and shear competed to govern our observed overturning length scale (less than or similar to 4 m) that were characterized by the Ellison length scale L-E. Only measurements closest to the seabed (1.7 m) were described by the log law-of-the-wall; generally both buoyancy and the presence of the bottom boundary influenced L-E, while sometimes flow-induced shear determined L-E. As the distance of our measurements from the seabed increased, the influence of buoyancy became more pronounced. These results highlight that a more general descriptor of the overturning length scale is necessary for complex stratified shear flows.
Original languageEnglish
Pages (from-to)C11017; 16pp
JournalJOURNAL OF GEOPHYSICAL RESEARCH-OCEANS
Volume116
DOIs
Publication statusPublished - 2011

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